In the search for a workable ankle arthroplasty, various designs have been tried. As seen below in Table 1, certain published results relating to conventional total ankle arthroplasty were disappointing for both patients and surgeons (the typical clinical series of Table 1 includes 20-40 patients followed for an average of five years or less; only general observations can be made from this data).
TABLE 1Good-to-Excellent Satisfaction Rates After TotalAnkle Replacements - Conventional Designs# ofAvg. F/UDeviceAuthor/YearAnkles(months)Satisfaction RateSmithDini/80212746%ICLHGoldie/82183660%TPRJensen/92235969%Bath & WessexCarlsson/93526081%TPRKumar/88376052%LCSBuechel/92407285%SmithKirkup/85188461%MayoKitaoka/9616010819%
As Table 1 reveals, patient satisfaction with conventional, cemented ankle implants has ranged from 19 percent to 85 percent (see, e.g., Dini A A, Bassett F H: Evaluation of the early result of Smith total ankle replacement. Clin Orthop 1980; 146:228-230; Goldie I F, Herberts P: Prosthetic replacement of the ankle joint. Reconstr Surg and Traumat 1981; 18:205-210; Jensen N C, Kroner K: Total ankle joint replacement: A clinical follow-up. Orthopedics 1992; 15:236-240; Carlsson A S, Henricson A, Linder L, Nilsson J A, Redlund-Johneur: A survival analysis of 52 Bath-Wessex ankle replacements. The Foot 1994; 4:34-40; Kumar D J R: Total ankle arthroplasty. A review of 37 cases. J Tn Med Assoc 1988; 81:682-685; Buechel F F, Pappas M, Iorio U: NJ low contact stress total ankle replacement: Biomechanical rationale and review of 23 cementless cases. Foot Ankle 1988; 8:270-290; Kirkup J: Richard Smith ankle arthroplasty. J Roy Soc Med 1985; 78:301-304; Kitaoka H B, Patzer G L: Clinical results of the Mayo total ankle arthroplasty. J Bone Joint Surg 1996; 78A: 1658-1664).
It is believed that length of follow-up was a major factor with patient satisfaction, as patients with longer follow-ups generally had declining degrees of satisfaction. As seen below in Table 2, the rates of radiographic loosening with these conventional implants were quite substantial, ranging from 22 percent to 75 percent (see, e.g., Goldie I F, Herberts P: Prosthetic replacement of the ankle joint. Reconstr Surg and Traumat 1981; 18:205-210; Jensen N C, Kroner K: Total ankle joint replacement: A clinical follow-up. Orthopedics 1992; 15:236-240; Carlsson A S, Henricson A, Linder L, Nilsson J A, Redlund-Johneur: A survival analysis of 52 Bath-Wessex ankle replacements. The Foot 1994; 4:34-40; Kumar D J R: Total ankle arthroplasty. A review of 37 cases. J Tn Med Assoc 1988; 81:682-685; Kirkup J: Richard Smith ankle arthroplasty. J Roy Soc Med 1985; 78:301-304; Kitaoka H B, Patzer G L: Clinical results of the Mayo total ankle arthroplasty. J Bone Joint Surg 1996; 78A: 1658-1664; Helm R, Stevens J: Long-term results of total ankle replacement. J Arthroplasty 1986; 1:271-277; Bolton-Maggs B G, Sudlow R A, Freeman M A R: Total ankle arthroplasty. A long-term review of the London Hospital experience. J Bone Joint Surg 1985; 67B: 785-790). Of note, it is believed that some of the major factors implicated with loosening were: 1) highly constrained designs; and 2) cement fixation (it might have been the use of cement alone, or the combination of the use of cement to create adequate space for cementation, which was a major contributing factor to increased loosening rates).
TABLE 2Radiographic Loosening After Total AnkleReplacement - Conventional Designs# ofAvg. F/UDeviceAuthor/YearAnkles(months)Loosening RateICLHGoldie/82183622%ICLHHelm/86145457%TPRJensen/92235952%Bath & WessexCarlsson/93526067%TPRKumar/88376026%ICLHBolton-Maggs/85416632%SmithKirkup/85188439%MayoKitaoka/9616010875%
Further, conventional total ankle arthroplasty has also been plagued with unusually high wound problems. The soft tissues around the ankle region, especially in rheumatoid and elderly patients, provide a relatively thin envelope for arthroplasty containment. Problems with superficial and deep infections, resection arthroplasties, attempted re-implantations or arthrodeses and, occasionally, below-knee amputations have dampened the enthusiasm of many orthopaedic surgeons involved with conventional total ankle replacement. In this regard, see Table 3 below, relating to published “long-term” results after conventional ankle arthrodesis.
TABLE 3Published “Long-Term” Results AfterConventional Ankle ArthrodesisAvg.Author/# ofF/UMajor **ContinuedHindfootYearPatients(years)ComplicationsPainDJDSaid/7836824%*>50% Mazur/79128*25%100% Morrey/8041848%76%50%Ahlberg/81411232%68%44%Boobbyer/8158921%**Morgan/851011010%**Lynch/8862734%**Glick/96348 6%**
While somewhat better short term results associated with conventional implants have stimulated interest in total ankle replacement, such conventional implants have shown their deficiencies. For example, one conventional prosthesis (the AGILITY ankle replacement) has shown an overall high rate of satisfaction in early follow up but with evident problems (see, e.g., Pyevich M T, Saltzman C L, Callaghan J J, Alvine F G: Total ankle arthroplasty: A unique design. Two to twelve-year follow-up. J. Bone Joint Surg., Vol 80-A(10):1410-1420, October, 1998; Saltzman C L, Moss T, Brown T D, Buckwalter J A Total Ankle Replacement Revisited. JOSPT 30(2):56-67, February, 2000; Saltzman C L, Alvine F G, Sanders R W, Gall R J. Challenges with Initial Use of a Total Ankle Clinical Orthopaedics and Related Research (Accepted)).
One issue in this regard is the large amount of bone that is typically resected during conventional surgery. This creates a problem if revision is required because the subsequent lack of bone makes revision or conversion to a fusion problematic. The difficulties caused by having to resect a large amount of bone will become more apparent over time as with longer follow up the need for revision becomes more common.
Another issue with this conventional AGILITY ankle replacement is the limited range of motion it allows after surgery. It is believed that in approximately fifty percent of the cases the patient's plantarflexion contracture remained with patients not being able to dorsiflex significantly beyond neutral position.
A second conventional prosthesis (the STAR), while believed to not require as much bone resection, has articular contact surfaces that are flat in the medial-lateral direction, thus making edge loading necessary when resisting the varus/valgus loads imposed upon the ankle during ordinary ambulation (see, e.g., Kofoed H, Danborg L: Biological fixation of ankle arthroplasty. Foot 1995; 5:27-3 1; Kofoed H, Toben S: Ankle arthroplasty for rheumatoid arthritis and osteoarthritis: Prospective long-term study of cemented replacements. J Bone Joint Surg 1998; 80B:328-332).
Further still, additional papers include the following: Morgan C D, Henke J A, Bailey R W, Kaufer H: Long-term results of tibiotalar arthrodesis. J Bone Joint Surg 1985; 7A:546-550; Glick T M, Morgan D D, Myerson M S, Sampson T O, Mann J A: Ankle arthrodesis using an arthroscopic method: Long-term follow-up of 34 cases. Arthroscopy 1996; 12:428-434; Morrey B F, Wiedeman G P: Complications in long-term results of ankle arthrodeses following trauma. J Bone Joint Surg 1980; 62A:777-784; Ahlberg A, Henricson A S: Late results of ankle fusion. Acta Orthop Scand 1981; 52:103-105; Mazur J M, Schwartz E, Simon S R: Ankle arthrodesis; long-term follow-up with gait analysis. J Bone Joint Surg 1979; 61A:964-975; Boobbyer G N: The long-term results of ankle arthrodesis. Acta Orthop Scand 1981; 52:107-110; Said B, Hunka L, Siller T N: Where ankle fusion stands today. J Bone Joint Surg 1978; 60B:211-214; Lynch A F, Bourne R B, Rorabeck C H: The long-term results of ankle arthrodesis. J Bone Joint Surg 1988; 70B:113-116.
Moreover, issued patents include the following: U.S. Pat. No. 6,183,519, entitled Ankle Prosthesis; U.S. Pat. No. 5,957,981, entitled Adjustable Prosthesis Joint; U.S. Pat. No. 5,824,106, entitled Ankle Prosthesis; U.S. Pat. No. 5,800,564, entitled Ankle Prosthesis With Angle Adjustment; U.S. Pat. No. 5,766,259, entitled Total Ankle Prosthesis And Method; U.S. Pat. No. 5,728,177, entitled Prosthesis With Foam Block Ankle; U.S. Pat. No. 5,312,216, entitled Artificial Joint Prosthesis; U.S. Pat. No. 5,156,630, entitled Ankle Joint Prosthesis Fixable In More Than One Orientation; U.S. Pat. No. 5,019,109, entitled Multi-Axial Rotation System For Artificial Ankle; U.S. Pat. No. 4,778,473, entitled Prosthesis Interface Surface And Method Of Implanting; U.S. Pat. No. 4,755,185, entitled Prosthetic Joint; U.S. Pat. No. 4,659,331, entitled Prosthesis Interface Surface And Method Of Implanting; U.S. Pat. No. 4,470,158, entitled Joint Endoprosthesis; U.S. Pat. No. 4,442,554, entitled Biomechanical Ankle Device; U.S. Pat. No. 4,360,931, entitled Prosthetic Ankle; U.S. Pat. No. 4,340,978, entitled New Jersey Meniscal Bearing Knee Replacement; U.S. Pat. No. 4,309,778, entitled New Jersey Meniscal Bearing Knee Replacement; U.S. Pat. No. 4,166,292, entitled Stressed Reinforced Artificial Joint Prosthesis; U.S. Pat. No. 4,156,944, entitled Total Ankle Prosthesis; U.S. Pat. No. 4,069,518, entitled Total Ankle Prosthesis; U.S. Pat. No. 4,021,864, entitled Ankle Prosthesis; U.S. Pat. No. D242,957, entitled Total Ankle Prosthesis; U.S. Pat. No. 3,987,500, entitled Surgically Implantable Total Ankle Prosthesis; and U.S. Pat. No. 3,975,778, entitled Total Ankle Arthroplasty.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. The figures constitute a part of this specification and include an illustrative embodiment of the present invention and illustrate various objects and features thereof.